Water Pollution

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Water Pollution


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Water Pollution

• Water Pollution is the addition of any substance
  that has a negative effect on water or the living
  things that depend on water.
• The substances that cause water pollution are
  called pollutants.

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Point source pollution

• Sources of pollution are classified, in
  part, by how they enter a body of water.
• Point source pollution is a specific
  source of pollution that can be identified.
• Example A pipe gushing colored water into a
  river       

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Nonpoint source pollution

• A widely spread source of pollution that cant be
  tied to a specific point of origin is called
  nonpoint source pollution.
• Example Runoff from a farm field, a street, or
  a construction site

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Effects of Pollutants

• Some pollutants can build up in the bodies of
  living things.
• Pesticides are chemicals intended to kill insects
  and other organisms that damage crops.
• An example of a pesticide is DDT.

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A very small amount of DDT in water can build up
to harmful levels in living things
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Major Sources of Water Pollution

• The three major sources of water pollution are
  human wastes, industrial wastes, and chemical
  runoff.

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Human Waste

• Sewage in cities
• During heavy rains or floods, sanitary sewers
  sometimes overflow and can pollute the surface
  water.
• If this happens, people are often told to boil
  water for drinking and cooking after a flood.
• The boiling kills many disease-causing organisms.

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Sewage in Rural Areas

• In rural areas, people must be careful where they
  locate septic tanks.
• If a tank is too near a stream or on a hill,
  wastewater can leak into the stream or flow
  downhill to the area of a well.

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Leaking septic tank
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Sewage in Rural Areas

• Wastes from cattle, pigs, and chickens can also
  be a problem in rural areas.
• Animal wastes can run off from pastures and
  barnyards and pass disease-causing bacteria and
  other kinds of pollution into bodies of water.

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Industrial Wastes

• Chemicals, smoke , and heated water are three
  types of pollutants produced by factories, mines,
  and other industries.

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Chemicals

• Many factory processes involve toxic chemicals
  and strong acids.
• Other toxic wastes are produced as a result of
  manufacturing and mining processes.
• Although laws control many point sources of
  chemical pollution, some factories still release
  toxic chemicals directly into nearby rivers and
  lakes.

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Chemicals

• Another problem is pollution caused by nonpoint
  sources.
• In the past, many industries stored toxic wastes
  in barrels or other containers buried
  underground.
• Over the years, however, many of these containers
  rusted or broke.
• The chemicals leaked out, polluting both the soil
  and the groundwater.

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Barrels of nuclear waste found in an abandoned
German salt mine
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Smoke and Exhaust

• Many power plants and factories burn coal or oil
  to fuel their processes.
• The engines of millions of cars, trucks, and
  buses burn gasoline.
• Smoke and exhaust from these sources pour into
  the air, especially around large cities.

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Smoke and Exhaust

• When coal, oil, and gasoline are burned, the
  gases sulfur dioxide and nitrogen oxide are
  released into the atmosphere.
• The sulfur and nitrogen react with water,
  forming sulfuric and nitric acids.
• The result is acid rain.

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Acid Rain

• Acid rain is rain or another form of
  precipitation that is more acidic than normal.
• Acid rain can affect fish, harm trees, and eat
  away the stone of buildings and statues.

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Heat Pollution

• Much of the water in factories is used to cool
  machinery or metal objects.
• The warm water alone can act as a pollutant.
• Many water organisms can live in only a narrow
  range of temperatures.
• Warm water released by factory into a nearby
  river or pond raises the temperature of the
  water, sometimes enough to harm the living things
  there.

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Chemical Runoff

• Farmers spread or spray fertilizing chemicals on
  their fields to produce better crops.
• When rain falls on the fields, it washes some of
  the chemicals away as runoff.
• Water used for irrigation also creates runoff.
• The fertilizers in the runoff are a nonpoint
  source of pollution.

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Examples of runoff
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Runoff from farms

• With the addition of fertilizers running off into
  ponds and lakes, the process of eutrophication
  speeds up.
• Runoff and irrigation water carry away pollutants
  from farm fields such as pesticides and
  fertilizers.

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Runoff from farms
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Runoff from roads

• When it rains, runoff carries oil into rivers and
  lakes, or underground and into the groundwater.
• During winter, runoff also picks up salt that is
  spread on roads and sidewalks to melt ice.
• Gasoline, oil, and salt are nonpoint sources that
  pollute rivers and lakes.
• They can also seep underground and pollute wells
  and aquifers.

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Water Pollution Solutions

• Solving pollution problems involves cleaning up
  existing problems as well as preventing new ones.
  
• Cleanup
• Many pollutants are removed from fresh water
  through natural cleanup processes.
• Living things in lakes, streams, and wetlands
  help reduce pollution by filtering out and
  breaking down waste materials.

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Living things helping cleanup pollution

• Examples
• Plant roots filter larger particles from the
  water.
• Certain bacteria consume oil and have been used
  to cleanup oil spills.
• Natural and artificial wetlands can be used to
  clean up water pollution.
• Wetlands have been built near coal mines to treat
  acidic mining runoff before it returns to the
  environment.

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Prevention

• Many industries have found that recycling
  techniques that conserve water also reduce
  pollution.
• For example, factories cool the water used to
  cool machinery and reuse it instead of releasing
  it into a river.
• Another example is when farmers collect and reuse
  the runoff water from their pasture as water for
  irrigation.
• Farmers can also plant fields of grasses that
  filter out pollutants before the water reaches a
  river or pond.